Method of and means for preventing offset



E. H. BUCY METHOD OF AND MEANS FOR PREVENTING OFFSET Jan. 3, 1939.

Filed May 15, 1936 Patented Jan. 3, 1939 UNITED STATES METHOD OF ANDMEANS FOR PREVENTING- 1 OFFSET Edmund H. Bucy,

Atlas Powder Company, Wilmington; corporation of Delaware ApplicationMay 15,

5 Claims.

This invention relates to a method of and or designs applied thereto bysimilar processes such as lithographing, rotogravure and the like, therehas heretofore been considerable diificulty in preventing the inkfromstaining surfaces with which it might come into contact.

Such surfaces may comprise thehands or clothing of persons handling suchstock, or adjacent surfaces of paper, cloth or the like, such as whenfreshly printed sheets are stacked or folded.

Previous methods of preventing such offsetting with which I am. familiarcomprise the application of. wax or parafline ina molten state to theprinted sheet of stock, such as disclosed in the patent to Grammer, No.1,445,273, of February I3, 1923, or the spraying of the sheet with asolution consisting of a fast drying solvent and a solute of the lacqueror cellulose derivative class, as disclosed in my copending application,Serial No. 582,919, filed December 24, 1931, and issued April 27, 1937,as Patent No. 2,078,790. Various other types of solutions having thedesired characteristics of solubility at room temperature in afast-drying solvent and capable of forming minute spacing globules orlands on the printed stock, for spray application to the sheet, havebeen employed.

The present invention is directed particularly to the mechanicalapplication of an anti-ofiset-.

ting medium to the printed stock by passing the 40 printed materialbetween rollers, one of which coats the material with theanti-ofisettingmedium by contact therewith.

It is a main object of the .present invention to provide a method ofapplying such anti-ofiset- 4,6 ting media tothe printed stock duringpassage of the stock past a given point by mechanical ,contact of amedium-carrying roll with the printed surface.

Another object of the invention is the provision of a means for applyingthe anti-offsetting medium in desired form to the printed stock, theapplying means being varied in accordance with the character oftheprinted stock and the protection desired against offsetting. so Theessential feature of my invention is the.

Stamford, Conn., assignor to Del., a

'1936, Serial No. 79,836

provision of a coating or applicating roller which is so formed on itssurface as to have a multitude of small depressions therein which varyin number, depending on the porosity of the paper which is being runthrough the machine. As the paper or similar stock contacts the roller,the medium carried in the depressions is deposited on the paper in theform of minute individual dots or lands. These lands are preferablytransparent so as not to interfere with the visibility of the printedmatter, and are quick-drying, so that as the paper leaves the roll theindividual lands form solid spacers, preventing adjacent surfaces comingin contact with the ink. The spacing between the lands allows the ink todry readily, and the anti-offsetting medium preferably is of suchcharacter as to be capable of being printed over in case of a multipleprinting process, such asin colorprinting and the like. Also, the mediumis preferably of such character as to .be in a partially dry or tackycondition as it contacts the printed stock, so that it is readilydeposited thereon and is practically dry as the paper stock progressesoff of the roller. 'Other objects and advantages of the presentinvention will be more apparent as this description proceeds, andreference is hereby made to the accompanying drawing,.illustratingdiagrammatically a preferred manner of carrying out the presentinvention, which, together with the specification, will disclose tothose skilled in the art the particular construction and operation ofthe present invention.

Considering the process now in detail, it'may be carried out byproviding a tank or receptacle 5, of any desired construction, which isadapted tocontain the anti-ofisetting medium as indicated' at 6. Thetank 5 is preferably provided with the cover I in order to preventevaporation of the medium, and the cover I, on one side of the roller 8which is journaled for rotation in the bearings 9 on opposite sides ofthe tank, is provided with an extended lip portion or scraper I0, whichhas scraping engagement with the surface of the roll 8, in order toremove excess liquid therefrom.

Any desired type of coating may be employed Six seconds nitro-cellulose(dry weight) lb 1 Dibutyl phthalate (liquid) oz 2 Liquid butyl acetateoz 26 Toluol oz 60 Ethyl acetate oz 40 As another typical. formula for acoating me dium of this type, I may employ the following: Ethylcellulose (approximately 48% ethoxy content) lb 1 Liquid toluol oz 78Liquid ethyl alcohol SD 1 oz 50 The specific viscosities of thenitro-cellulose or ethyl cellulose which might be employed in suchformulae are not by anymeans critical, but are typical only. Other solidmaterials may be employed in the solution.

The liquids which may be employed for this purpose may comprise anysolid or semi-solid substance which may be dissolved in a volatilesolvent or a mixture of volatile solvents in the form of solution, butpreferably restricted to essentially transparent solutions so as not tointerfere with any image which may have been placed on the paper duringthe printing, lithographing, or other similar operations prior to theapplication of the anti-offset medium.

Obviously, wax or paraffine in the molten stage may be employed inconnection with this process if desired, or other solutions such as setforth in my above mentioned copending application may be employed ifdesired.

Referring again to the diagrammatic illustration on the process, theroll 8 is provided in its' lateral surface with a plurality ofindividual small depressions, or the surface may be corrugated. Thedepth of the depressions varies, depending upon the porosity of thepaper which is to be run through the machine, while the spacing of theindividual depressions may also vary. For example, in the application ofthis medium to newsprint, I find that probably thirty depressions to thelinear inch will be suflicient, while on certain types of magazinestocks, perhaps as many as 200 to 300 depressions per linear inch may berequired in order to deposit the proper amount of anti-offsettingmedium.

The lip H) of the cover for thereservoir 5 scrapes the surface of theroll as the roll is rotated about its axis, removing any excess mediumwhich may be clinging to the surface of the roll, and the lacquer orother coating material is thereby retained in the bottom of'each of thesmall depressions. This prevents the application of a continuous film ofthe lacquer or other offsetting medium to the paper, and also insuresthat the medium will be deposited on the .paper in the form ofindividual spaced minute particles. Preferably the scraping knife or lipis made adjustable in order to vary the effective pressure thereofagainst the surface of the roll 8.

A squeezing roller I2 is provided and is journaled for rotation inalignment with the roll 8, whereby the paper or other stock is fed tothe machine between the two rollers, and is firmly pressed against thesurface of the roll 8 during this process.

The rollers 8 and I! are driven in such manner that their surface speedwill be synchronized with the speed of the device which feeds the papertherebetween.

Due to the evaporable nature of the solvent in which the cellulose orother solid or semi-solid medium is dissolved, as the roller 8 rotatesaway from the scraping surface 10 and into contact with the paper sheetl3 passing between the rolls 8 and l2, 9. portion of the solventevaporates, so

that the material in the depressions of the roll 8 may be in a slightlytacky oradhesive condi- 'tion, which will assist in transferring thismaterial from the depressions in the roll 8 to the contacting surface ofthe sheet of stock l3. As the stock passes between the rollingengagement between the rolls 8 and I2, this medium is deposited on thesheet in the form of small indi vidual particles or lands, which,immediately upon deposition, begin to harden due to the evaporation ofthe solvent carrying the same, and consequently as the sheet moves awayfrom the rolls, these small globules or lands harden into individualspacers which serve to prevent the paper and other substances fromcontacting engagement which would producerubbing against the ink whichmay not have dried on the paper. Thus, when sheets, such as the sheetsl3, are

stacked or passed into folding and cutting rolls,

the individual spacers will prevent rubbing of the freshly pn'ntedsurfaces, and will thus protect the sheets against what is termedoffset.

It is to be understood that regardless of the type of solution which isemployed in the reservoir 5, and which is contained in the smalldepressions in the surface of the 'roll 8, the solution must have thecharacteristic of drying ratherrapidly, if it is in the form of a solutedissolved in a volatile solvent, or of solidifying rapidly if it is inthe form of a wax heated to a molten state. This is in order to insurethat after the paper l3 has passed through the rolls, it will notrequire any considerable length of time before the individual solidspacers are formed, these being indicated at H on the sheet i 3 after itpasses through the rolls.

While the depressions may be formed in any desired manner on the roll 8,such asby corrugating the roll or the like, I find that one manner inwhich this can be accomplished and which will produce excellent resultsis by engraving the surface of the roll to form the individualdepressions which are generally indicated at l5 in the drawing.

It is obvious that other arrangements of the roll may be provided forapplying the medium to the surface of the freshly printed stock, andthat various types of reservoirs and scraping surfaces may be employed.Also, the paper may be passed through the rolls in the form of singlesheets, instead of in the form of a continuous strip, or in any othermanner as is usual in connection with the printing processes.

The medium employed should also have the characteristic of'being capableof allowing the sheet to be reprinted,'since in certain printingprocesses it is desired to accommodate such reprinting of the sheet, asfor example in color printing, in which several different colors aresuccessively printed on the sheet to form a colored design or the like.

I therefore do not intend to be limited to t!- exact means shown anddescribed for carrying 1. The method of preventing offset which comprises providing a rolling surface having minute depressions therein,moving said surface through a substantially transparent solutioncomprising a cellulose derivate and an evaporable solvent,

removing said solution from said surface while allowing minute globulesthereof to remain in said depressions, exposing the globules to theatmosphere for a time sufilcientto evaporate a portion of the solventand bring the globules into a tacky condition, passing .a printed sheetinto contact with said surface, and simultaneously transferring the saidglobules to said sheet during said contact, the consistency and spacingof the globules being such that they remain discrete on the sheet.

2. The method of preventing offsetting ,of

printed surfaces, which comprises printing upon a surface, formingseparated globules of a substantially transparent volatile cellulosicsolution arranged in predetermined spaced relation, ex.- posing saidglobules to the atmosphere sumciently to render them tacky, and applyingsaid globules in their tacky condition to the printed surface whilemaintaining them in said predetermined,

spaced relation, thereby causing said globules to adhere to said surfacein said spaced relation, the consistency of said globules when soapplied to said surfacebeing such that they remain discrete thereonin'said spaced relation with the'intervening areas of the printedsurface exposed to atmosphere to facilitate drying of the printedsurface.

.3. The method of preventing offset which comprises; providing a rollingsurface having minute depressions therein, moving said surface through asolution comprising a cellulose derivative and an evaporable solvent,removing said 'solution contact with said surface, and simultaneously Itransferring said globules to said sheet during said contact, theconsistency and spacing of the globules being such that they remaindiscrete on the sheet.

4. The method of preventing offset which comprises; providing a rollingsurface having minute depressions therein, moving said surface through aliquid capable of being formed into tackyglobules, removing from thesurface the excess of liquid which does not fill the said depressions.allowing the globules of liquid in said depressions .to become tacky,passing asheet upon which offset is to be prevented into contact withsaid surface and simultaneously transferring said globules to said sheetduring said contact, the consistency and spacing of the globules beingsuch that they remain discrete on .the sheet.

5. The method of preventing offsetting of printing surfaces whichcomprises; printing upon a surface, forming in predetermined spacedrelation separated globules of a solution of a cellulose derivative in avolatile solvent, removing sufficient'solvent from said globules so thatthe globules assume a tacky condition and applying said globules intheir taclw condition to the printed .surface while maintaining them insaid predeterthe intervening areas of the printed surface exposed -tofacilitate drying of the printed surface.

. EDMUND H. BUCY.

